Indicating fuse-plug



O. W. FELDMANN INDICATING FUSE PLUG Filed April 16, 1930 0270 WfELDMHN/Y' INVENTOR ATTORNEY Patented Mar. 15, 1932 UNITED STATES PATENT? OFFICE OTTO W. FIE ILDIIHLALN'IIQ', OF RICHMOND HILL, NEW YORK INDIGATING FUSE-PLUG- Applieation filed April 16, 1930. Serial No. 444,803.

m is insufficient to melt the fuse, so that the fuse element will break without the formation of globules during burning of the fuse slightly below the fuse elements melting point.

Still another object is to construct the fuse so that the indicating element may be forcibly ejected by means of an ejecting spring, when the fuse has been ruptured, the indicating element being normally held in non-indicating position by a retaining spring of less tension than the ejecting spring.

A further object is to construct the interior of the fuse body with receptacles or chambers for the ejecting spring and retaining spring so that the fuse element will not be in danger of being sheared off by the ejecting spring, in

case the spring is turned during the manufacturing operation.

A still further object is to construct the fuse so that assembly of the same will be fa- ;5 cilitated during manufacture, the construction being such that the fuse element may be inserted first, and the ejecting spring subsequently hooked on to the fuse as the parts are assembled.

Yet another object is to construct the indicator so that there will be no possibility of the same jamming or failing to indicate when a fuse has blown, the outer cap or other part of the fuse body being preferably equipped with guiding means for the indicator so that the same will be positively ejected.

Other objects are to'simplify and improve the construction of fuse plugs generally and reduce the cost of manufacture thereof.

Other objects and advantages of the invention will be hereinafter specifically pointed out or will become apparent, as the specification profzeeds.

With the above indicated objects in view,

the invention resides in certain novel constructions and combinations and arrangement of parts, clearly described in the following specification and fully illustrated in the accompanying drawings, which latter show embodiments of the invention as at present preferred.

In said drawings:

Fig. l is a bottom plan view of the plug;

Fig. 2 is a side elevation of the plug, bottom end up;

Fig. 3 is a longitudinal sectional view, substantially on the line 33 of Fig. 2 looking in the direction of the arrows, showing the interior parts in normal position.

Fig. 4 is a view similar --to Fig. 3 showing the indicator in its ejected position; and

Fig. 5 is to a top plan view of the plug.

The self-indicating fuse plug 10 in the. present instance includes a body portion 11 preferably formed of porcelain or other insulating material, this body portion preferably having a generally downwardly tapering contour, to facilitate manufacture of the same. This body 11 is provided with an elongated axial fuse chamber 12; and a transverse opening 13 leads from the fuse chamber 12 to the outer side of the plug body 11. The lower end of the plug body 11 is provided with a center contact 14; and to the neck portion 15 of this center contact 14, which neck portion preferably extends into the fuse chamber 12, the fuse element 16 is attached. This fuse element 16 preferably consists of a strip or the like of fusible material. The fusible element 16 is positioned in the chamber 12 so that a loop portion 17 is formed adjacent to the transverse opening 13 and the free end of the fuse element 16 is passed through this opening to the outer side of the plug body 11 as seen at 18. This free end of the fuse element is secured in place at the outer side of the body 11 by means of the shell 19 which is formed with screw threads 20 corresponding to the screw threads 21 formed about the body 11. Any excess length of the fuse element pro'ecting beyond the lower end of the shell as in 'cated at 18 is removed and the opposite ends of the fuse may be soldered to the center contact 14 and shell 19. Thus,

as stated hereinabove the fuse element 16 is put in place as the first step in the assembly of the parts of the plug; that is, before the indicator or the indicator ejecting means are inserted. The shell 19 and center contact 14 serve to place the fuse element 16 in the circuit in the manner customary with fuses of the plug type.

Means are provided to positively indicate the breakingof the fuse due to. overload, short circuitin or the like in the electrical circuit; and in t is instance said means include an indicator 22 having a head portion 23 and a stem 24. This indicator 22 is positioned in an enlarged bore 25 formed at the outer end of 20 the plug-body 11, this outer end of the plug body being closed by a cap 26, this cap 26 having a rearward portion 27 preferably turned over the outer rim 28 of the plug body during the course of manufacture. To secure as the cap in place against rotation relative to the plug body 11, the outer rim 28 of the plug body may be provided with a plurality of indentations 29 into which the rearwardly turned portion 27 of the cap 26 may be de- 3o pressed; and the outer surface of the portion 27 may be provided with a knurled surface to facilitate insertion of the plug into and its removal from, its socket. The body 11 is also preferably provided with substantially 335 similar indentations 39 into which portions of the shell 29 may be pressed, to securely its lower end with a hook portion 37 adapted to be hooked over the loop ortion 17 of the fuse element 16. The com ined tension of the retaining spring 33 and fuse element 16 is just sufficient to overcome the force of the ejector spring 34, which as will thus be understood is of greater tension than the, retainin spring 33.

hen the fuse element 16 has become weakened due to an overload orshort circuiting of an electrical circuit, whether such weaken-- ing is only partial, or a complete fusing or melting of the fuse element, 16, the ejectorspring 34, released from the fuse, and being of greater tension than the retaining spring 33, will forcibly eject the indicator 22 from the position seen in Fig. 3 to the position shown in Fig. 4. The stem 24 will thus project beyond the outer surface'of the cap 26, where the same can be readily seen,or felt, to indicate the fuse that has burned or blown. The outer end of the stem 24 may be provided with suitable insignia 38, which may be the manufacturers trade-mark or any other desired device.

- 'An important feature of the present construction is the facility of assemblage of the parts. As already stated the fuse element 16 is first put in place. Then, the ejector spring 34 is inserted in the chamber 35, and the hook portion 37 at the lower end "of the ejector spring is hooked over the looped portion 17 of the fuse element. The retaining spring 33 is then applied around the-stem 24, and the cap 26 .is then put in place and secured. The 100 arrangement of the shoulder 36 and transhold the shellinplace. The cap 26 in ,thismyerse passage 13 is such that the fuse element instance has an axial aperture 30 adapted to receive the end of the stem 24; and the portion of the cap 26 forming the annular wall of p the aperture 30 is preferably turned inward: 1y as seen at 31 to afford a guide for the stem 24 whereby the stem is maintained in proper position for positive ejectment, and is guided during its travel during the ejecting movement. The indicator 22, in'the normal position of the interior parts of the plug, rests against a shoulder 32 formed at the base of the chamber 25, and the indicator is retained in this normal position by means of a coil spring 33 adapted to act between the inner side of the cap 26 and the outer side of the head 23 of the indicator. I

Means are provided to eject the indicator upon breaking of the fuse, and in this instance said means include an ejector spring 34 pro vided at the inner side of the head portion 23 o'fthe indicator,,this ejector spring 34 being positioned in a bore 35', this bore 35 being of smaller diameter than the outer chamber 25, and of slightly greater diameter than the fuse chamber 12. Thus a shoulder36 is formed at the base of the ejector spring chamber 35, against which the ejector spring is adapted to bear. The ejector spring is provided at 16 is not likely to be sheared off during the assembly of the parts. The attachment of the fuse element 16 as the first step in the I manufacture is a distinct advantage over former types of fuses since it eliminates the difficulty usually attendant uponinserting the fuse element as the last step in assembling the parts.

The indicator 22.is made of insulating material so that there is no danger of short-circuiting or electrical! disturbance within the fuse, or at the exterior thereof. Also, it is to be understood that While I preferably insert the fuse element as a first step in assembling the parts, the fuse elements may also be inserted last if desired. Furthermore, the transverse opening 13 is'desirably formed at a cut out portion of the shoulder 36, so that the insertion of the fuse element is thereby facilitated.

The hereinbefore described construction admits of considerable modification without departing from the invention;therefore, it 1 is the Wish not to be limited to the precise arrangements shown and described, which are as aforesaid, by way ofillustration merely. In other words the scope of protection contemplated is to be taken solely from the appended claims, interpreted as broadly as is consistent with the rior art.

, What, claim is:

1. A self-1ndicating fuse including a body portion-formed of insulating material said body having a bore and a transverse fuse opening extending through a wall of said body, a center contact at the base of said body in axial alignment with said elongated bore, a fusible element having one of its ends secured to said center contact, the opposite end of said fusible element extending through said transverse opening and being secured at the outer'side of said body, an indicator at the forward end of said body, an ejector spring normally compressed between said indicator and said shoulder, said ejector spring having a portion normally in engagement with said fusible element, and a retaining spring at the front of said indicator head.

. 2. A self-indicating fuse including a body portion formed of insulating material said body having an internal bore and a transverse fuse opening extending through a wall of said body to said bore, a center contact at the base of said body in axial alignment with said elongated bore, a shell secured at the outer side of said body, a fusible element having one of its ends secured to said center contact, the opposite end of said fusible element extending through said transverse *opening and 'beingsecured between said shell and said body, an indicator at the forward end of said body, a resilient ejector member nor mally compressed behind said indicator, said ejector normally in engagement with said fusible -element, a retaining spring at the front of said indicator and an outer cap at the front of said body, said cap having an axial opening for said indicator when ejected by rupture of said fusible element.

3. A self-indicating fuse including a body portion formed of insulating material said body having 'an elongated plural diameter bore and a transverse fuse opening extending through a wall of said body, a center contact at the base of said body in axial alignment with said elongated bore, a screw threaded shell secured at the outer side of said body, a fusible element having one of its ends secured to said center contact, the opposite end I of said fusible element extending through said transverse opening and being secured between said shell and said body, said bore including a larger diameter chamber forming a shoulder forward of said elongated chamber, an indicator at the forward end ofsaid body, an ejector device between said indicator and said shoulder, said ejector device normally secured to said fusible element, a retaining spring at the front of said indicator head, an outer cap at the front of said body,

said cap having an axial opening, and'the wall of said opening including an inwardly extendin 'dingrim for said stem when ejected b? I I I I JtHIB of said fusible element.

4. A self-indicating fuse including a body portion having a bore and a transverse fuse opening extending through a wall -of said body, a center contact on said body, a shell secured at the outer side of said body, a fusible element haying one of its ends secured to said center contact, the opposite end of said fusible element extending through said transverse opening and being secured between said shell and said body, an indicator forward of said fusible element, an ejector spring normally compressed behind said indicator, said indicator including a head and a stem, said ejector spring having a portion normally in engagement with said fusible element, a retaining spring at thefront of said indicator head, an outer cap at the front of said body, said cap having an axial opening, the wall of said opening including an inwardly ex-- tending guiding rim for said stem when ejected by rupture of said fusible element.

5. A self-indicating fuse including a body portion formed of insulating material, said body having an elon ated plural diameter bore and a transverse use opening extending through a wall of said body, a center contact at the base of-said body in axial alignment with said elongated bore, a screw threaded shell secured at the outer side of said body, a fusible element having one of its ends secured to said center contact, the opposite end of said fusible element extending through said transverse openin and being secured between said shell and said body, said fusible element including a looped portion,

said bore including a larger diameter chamber forming a shoulder forward of said elongated chamber, an indicator at the forward end of said body, an ejector spring normalsignature.

" OTTO W. FELDMANN. 

